I am building a web application on my MacBook Pro which needs to send email. When the application attempts to send, the connection times out. I am running postfix and I I followed the directions found here.

To troubleshoot the server, I used telnet to manually connect to localhost on port 25. I was able to connect to it successfully, but I received no response as I typed commands. Here is a transcript.

Just comment out the imap_submit_cred_file = /etc/postfix/submit.cred in the /etc/postfix/main.cf file. Then you don't have to configure any usernames and passwords. And Postfix listens to localhost only by default.